To provide an image forming system reducing the color material consumption of an image forming device and uniforming it as much as possible by limiting the color material consumption in according to a situation of each division.

A message creating means 36 for creating a color conversion message for reducing cumulative color material consumption with respect to input image data is provided in an image forming part side, and a setting means for presetting whether or not to carry out color conversion to a recommended color in according to the situation of each division is provided at a host computer side. If there is a bias in the color material consumption of the input image data, the message is displayed in a computer of a user who can allow color limitation, and color conversion is automatically carried out. The message is not displayed in a computer of a particular division wherein limitation is difficult, and color conversion is not carried out, too.